So far I'm impressed by the AI.
Yes the passive bug is slightly annoying but luckily it doesn't happen all the time.
What I'm most impressed about is how it handle itself in seiges.
They switch troops to counter the threat properly(They use archers at the beginning but when you get close they switch and send up melee troops to counter your troops scaling the walls).
They fall back to the different rings when the previous one has been over run.
So much better then the seige AI in RTW.